A xen server that was in a resource pool became corrupted and lost all nic/network information & needed to be reinstalled from scratch. After reinstalling it, there were duplicate server entries in the pool within the XenCenter console, one was the new server that was reinstalled and added back into the pool, the other was the old ghost entry that was no longer valid. There was no way to remove this lost entry from the XenCenter console. The way to do this is shown below using the xe command.

On the PC with XenCenter installed first get the uuid of the lost host by doing pool-sync-database. You need to connect to the pool master host ip:

C:\Program Files\Citrix\XenCenter>xe -s 10.10.1.25 -u root -pw PASSWORD pool-sync-database
You attempted an operation which involves a host which could not be contacted.
host: 1500f12e-54c6-4d23-b1ab-88ff5216c0d1 (ubcxensrv5)

Next, use the host-forget command to remove the host.

C:\Program Files\Citrix\XenCenter>xe -s 10.10.1.25 -u root -pw PASSWORD host-forget uuid=1500f12e-54c6-4d23-b1ab-88ff5216c0d1
WARNING: A host should only be forgotten if it is physically unrecoverable;
WARNING: if possible, Hosts should be 'ejected' from the Pool instead.
WARNING: Once a host has been forgotten it will have to be re-installed.
WARNING: This operation is irreversible.
Type 'yes' to continue
yes
Read yes

We ended up getting one of the two to go away by unplugging the network cables from all the other boxes except the master and trying the above commands again. But I honestly don’t know if that is what removed them or not.